The present invention relates to transistors and a method for manufacturing transistors of a first and second type, in particular thin-film transistors, on a substrate, and a transistor configuration.
Integrated circuits, in particular CMOS circuits, are manufactured using a large number of process steps. The manufacturing costs of these circuits are determined by the process complexity and the processing time. Highly-complex components often require many hundreds of individual process steps and take many days to complete the process for the product. Some of the process steps must be devoted to producing the individual active components. For example, at least six masking steps are required to manufacture CMOS transistors using conventional methods. One masking step is required to pattern each of the following:                the channel,        the n+ drain/source areas (contact areas of a first type of transistor);        the p+ drain/source areas (contact areas of a second type of transistor);        the gate electrode;        the contact holes through a gate dielectric;        the contact metallization.        
In the related art, LDD (lightly doped drain) areas adjacent to the drain-source areas often require an additional mask.
A method of this type is made known in US 2004/0197967 A1, for example. Areas for transistors of a first and second type are defined on a substrate; this is where n-channel and p-channel transistors will be subsequently produced. The first mask is used to define the semiconductor islands in which the transistor channels will be located.
The gate dielectric is now deposited, and a second photomask and doping are used to create the drain/source areas of the n-channel transistors, and a third photomask and doping are used to define the drain/source areas of the p-channel transistors. The gate metallization is now placed on this, and it is patterned using the fourth mask. An intermediate insulation is subsequently deposited, into which holes are etched, using the fifth mask. These holes are filled with a metal, and they are patterned for metallization, using a sixth mask.
It is always desirable to have the fewest number of process steps and masking steps possible in a process, in order to reduce the manufacturing costs and throughput time.